The present invention relates to a novel fiber-reinforced chlorinated polyethylene composition and a process for producing said composition. More particularly, the present invention relates to a fiber-reinforced chlorinated polyethylene composition comprising a chlorinated polyethylene and a polyamide of fine short fiber form dispersed in the chlorinated polyethylene as a reinforcing agent, which is superior in mechanical properties, fatigue resistance, heat resistance and processability and which can be suitably used in various products requiring chlorinated polyethylene, as well as to a process for producing said composition.
Chlorinated polyethylenes vary from those which are noncrystalline or microcrystalline, have rubber elasticity and are soft, to those which are semicrystalline and hard plastic-like. In general, chlorinated polyethylenes have good characteristics in flexibility, weather resistance, oil resistance, chemical resistance, electrical properties, flame retardancy, self-extinguishing property, processability, and compatibility with other polymers, and are in wide use in various products as a base rubber, a base resin or a modifier for other polymers.
Examples of the application of chlorinated polyethylene include hoses, sheets, roofings, wire coatings, parts for automobiles, electrical parts, and impact resistance and/or flame retardancy improvers for polyvinyl chloride, polyethylene, polypropylene, polystyrene, ABS resin, etc. However, in using a chlorinated polyethylene in these applications, the mechanical properties (e.g. rigidity, strength) and heat resistance are insufficient in some cases; therefore, it has been desired to improve the mechanical properties and heat resistance of chlorinated polyethylene without sacrifying its processability.
In order to improve the mechanical properties of a resin or a rubber, it is most generally conducted to add thereto an inorganic filler or carbon black. This improvement usually requires a large amount of the additive and, in many cases, the improvement effect is still insufficient. Increase in addition amount for higher reinforcement effect results in reduced fluidity, dispersibility and processability, or in greatly reduced mechanical properties (e.g. strength, elongation, impact resistance). Thus, the addition of inorganic filler or carbon black has a restriction in addition amount or reinforcement effect.
For more effective reinforcement, there is a reinforcement using a fibrous reinforcing agent. There have been studied and proposed various fiber-reinforced compositions obtained by adding to a base resin or rubber an inorganic fiber of glass, ceramic or the like, or an organic fiber of cellulose, polyester, polyamide, liquid crystal polymer or the like. In these compositions, the addition of a relatively small amount of a fiber can increase rigidity; however, dispersibility and fluidity are reduced, and the molded articles produced from the compositions have surface roughening, reduced processability and, when undergoing a large deformation, insufficient fatigue resistance. These problems are attributed to the relatively large diameter (generally 0.01 mm or more) and rigidity of fiber, which is a detrimental drawback when it is intended to reinforce a resin or rubber having flexibility (e.g. chlorinated polyethylene) without sacrifying the flexibility. Further, since the fiber has a relatively large diameter, the fiber's total surface is small when the fiber is added in a given amount, and resultantly the compatibility between the fiber and the resin or rubber to be reinforced is insufficient. This is considered to be another reason for the above problems.